Method of producing a hermetic reclosable package using seal bars with non-parallel geometry

ABSTRACT

A method and apparatus is disclosed which include a pair of opposed seal bars for the manufacture of reclosable packages. The method and apparatus are particularly adaptable to form fill seal manufacture of reclosable packages. The first opposed seal bars includes a concave metal sealing surface and the second opposed seal bar includes a rubberized or otherwise deformable sealing surface. This allows a hermetic seal to be formed across an abrupt transition of thickness of material between the opposed seal bars, such as when a zipper ends adjacent to a side seal in a reclosable bag.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method an apparatus for hermetically sealing a zipper into a reclosable package. In particular, the present invention relates to a pair of seal bars with a first seal bar which has a rubberized and deformable sealing surface and a second seal bar made of metal and concavely shaped in order to apply a greater sealing pressure at the ends of the seal bar, which is the area which typically intersects the side seals of the reclosable package.

2. Description of the Prior Art

In the prior art, methods and apparatus for the manufacture of reclosable packages are well developed and satisfactory for their purposes. Form fill seal methods and apparatus are particularly suitable for the manufacture of reclosable packages.

Many applications require that the seals in a reclosable package be hermetic. However, when a flanged zipper is used, both the seal of the zipper to the package and the seal of the package walls to each other (particularly immediately adjacent to the cut ends of the zipper) must be hermetic. In particular, this may occur when a zipper is applied transversely to a film, before the zipper film is introduced to a form fill seal apparatus. In the form fill seal apparatus, the film is folded around the zipper ends and the film edges are sealed together in a side seam. As the zipper may be shorter than the front panel of the package, this often leaves a small gap between the side folds of the film and the zipper ends. The subsequently required hermetic sealing involves two different thicknesses of material, as well as the abrupt transition therebetween. This can be difficult using prior art seal bars, wherein both seal bars of an opposed pair are made of metal with interlocking teeth, using conducted heat to activate the sealant layers.

Commonly assigned U.S. patent application Ser. No. 11/449,999, entitled “Method and Apparatus for Hermetically Sealing a Zipper Into a Reclosable Package”, filed on Jun. 9, 2006 by Wihlborg and Howell discloses a pair of seal bars wherein one of the seal bars includes a rubberized surface to accommodate the differences in thicknesses which may be encountered in forming a seal. While this has been satisfactory for its intended purposes, further improvements are sought in increasing the quality of the hermetic seal at the ends of the seal line.

OBJECTS AND SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide seal bars and a method of use thereof, particularly for form fill seal or similar apparatus, for the manufacture of reclosable packages, wherein the seal bars provide hermetic seals along a seal line with various thicknesses of material, specifically maintaining an improved hermetic seal at the ends of the seal line.

It is therefore a further object of the present invention to provide seal bars and a method of use thereof, particularly for form fill seal or similar apparatus, for the manufacture of reclosable packages, wherein the seal bars can provide hermetic seals along a seal line with abrupt transitions in thicknesses of material.

It is therefore a still further object of the present invention to provide seal bars and a method of use thereof, particularly for form fill seal or similar apparatus, which are easily adaptable into existing apparatus without substantial modification.

These and other objects are attained by providing a pair of opposed seal bars wherein a first seal bar has a rubberized and deformable sealing surface so as to maintain contact with the web material notwithstanding different thicknesses and possible abrupt transitions therebetween and wherein a second seal bar is metal. The second seal bar is concave shaped in order to apply additional pressure at the ends of the seal lines so as to maintain the hermetic quality of the seal. Typically, the width of the jaw face of the first and second seal bars is reduced and the sealing surface has a geometry to make a seal line in a controlled pattern. This may be used in combination with a peel seal to improve the quality of the seal. The peel seal and the flange-to-package seal may be co-extensive across the length of the package or may be co-extensive only near the side seals.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects and advantages of the invention will become apparent from the following description and from the accompanying drawings, wherein:

FIG. 1 is a top plan view of the seal bars of the present invention.

FIG. 2 is a plan view of a reclosable package or bag, showing a seal line which would typically be formed by the seal bars of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings in detail wherein like numerals indicate like elements throughout the several views, one sees that FIG. 1 is a top plan view of the first and second opposed seal bars 12, 14 of the present invention. Reclosable package 100 is illustrated between first and second opposed seal bars 12, 14. First and second seal bars 12, 14 are brought together in a relative reciprocating motion to form a seal line 102 (see FIG. 2) on reclosable package 100.

First seal bar 12 includes an outward metal support portion 16 and an inward rubberized portion 18. The outward metal support portion 16 typically includes heater elements (not shown). The inward rubberized portion 18 presents a sealing surface with sufficient elasticity to allow for variations in the width of the material in the seal line of the reclosable package 100.

Second seal bar 14 is typically comprised of metal and presents a concave sealing surface 20 wherein the ends 22, 24 are closer to the first seal bar 12 than is the central recessed area 26. This configuration permits a seal line to be formed wherein a higher pressure is applied between the first and second seal bars 12, 14 at the ends 22, 24 than at the central recessed area 26. This provides for a higher reliability and quality of the hermetic seal at the ends of the seal line.

FIG. 2 is a plan view of a typical reclosable package 100 which includes a seal line 102 formed by first and second seal bars 12, 14. Reclosable package 100 includes co-extensive front and rear sheets 104, 106 of web or film sealed along the bottom 110, sides 112, 114 and top 116. The top 116 forms a removable header 118 which is formed over zipper 120 which is in the interior formed between sheets 104, 106. Zipper 120 typically has first and second flanges which are sealed to the interior of respective front and rear sheets 104, 106 along seal line 102. Zipper 120 typically has a width somewhat less than that of front and rear sheets 104, 106 of web or film. The concave curvature of second seal bar 14 allows for increased pressure along the ends of seal line 102, thereby increasing the hermetic quality and reliability of the seal along seal line 102.

Thus the several aforementioned objects and advantages are most effectively attained. Although preferred embodiments of the invention have been disclosed and described in detail herein, it should be understood that this invention is in no sense limited thereby and its scope is to be determined by that of the appended claims. 

1. A pair of opposed seal bars including a first seal bar and a second seal bar, wherein the first seal bar has a concave sealing surface.
 2. The pair of opposed seal bars of claim 1 wherein ends of the first seal bar are closer to the second seal bar than is a central area of the first seal bar.
 3. The pair of opposed seal bars of claim 1 wherein the second seal bar has a deformable sealing surface.
 4. The pair of opposed seal bars of claim 3 wherein the deformable sealing surface is rubberized.
 5. The pair of opposed seal bars of claim 1 wherein the first seal bar includes a metal sealing surface.
 6. The pair of opposed seal bars of claim 1 wherein at least one of the first and second seal bars is heated.
 7. The pair of opposed seal bars of claim 1 wherein the first and second seal bars are heated.
 8. The pair of opposed seal bars of claim 1 wherein the first and second seal bars have a reciprocating relationship with respect to each other.
 9. The pair of opposed seal bars of claim 1 wherein the deformable sealing surface is adapted to accommodate a transition in thickness from a side seal between first and second sheets of web to a zipper engaged between the first and second sheets of web adjacent to the side seal.
 10. The pair of opposed seal bars of claim 1 wherein the deformable sealing surface is adapted to accommodate a transition in thickness from a side seal between first and second sheets of web to a zipper engaged between the first and second sheets of web adjacent to the side seal, wherein the zipper includes a first and second profile with a peel seal therebetween.
 11. A pair of opposed seal bars including a first seal bar and a second seal bar, wherein the first seal bar has a concave sealing surface; and further including first and second sheets of web with a zipper between the pair of opposed seal bars.
 12. The pair of opposed seal bars of claim 11 wherein ends of the first seal bar are closer to the second seal bar than is a central area of the first seal bar.
 13. The pair of opposed seal bars of claim 11 wherein the second seal bar has a deformable sealing surface.
 14. The pair of opposed seal bars of claim 13 wherein the deformable sealing surface is rubberized.
 15. The pair of opposed seal bars of claim 11 wherein the first seal bar includes a metal sealing surface.
 16. The pair of opposed seal bars of claim 11 wherein at least one of the first and second seal bars is heated.
 17. The pair of opposed seal bars of claim 11 wherein the first and second seal bars are heated.
 18. The pair of opposed seal bars of claim 11 wherein the first and second seal bars have a reciprocating relationship with respect to each other.
 19. The pair of opposed seal bars of claim 11 wherein the deformable sealing surface is adapted to accommodate a transition in thickness from a side seal between the first and second sheets of web to the zipper engaged between the first and second sheets of web adjacent to the side seal.
 20. The pair of opposed seal bars of claim 11 wherein the deformable sealing surface is adapted to accommodate a transition in thickness from a side seal between the first and second sheets of web to the zipper engaged between the first and second sheets of web adjacent to the side seal, wherein the zipper includes a first and second profile with a peel seal therebetween. 